Power saving circuit of LCD unit

Abstract

To realize power saving of an LCD unit according to VESA standard with a low cost, a power saving circuit of the invention comprises screen control means (2, 3, 4) for turning off a back-light of the LCD (5) and stopping display data to be supplied to the LCD, when a vertical synchronous signal output by the LCD control circuit is suspended for a first fixed time; and power control means (6, 7) for stopping a power supply of the LCD, when a horizontal synchronous signal output by the LCD control circuit is suspended for a second fixed time.

What is claimed is: 
     
       1. A power saving circuit of an LCD unit having an LCD, said power saving circuit comprising: an LCD control circuit according to a VESA (Video Electronics Standards Association) standard, for controlling the LCD;   a screen controller for turning off a back-light of the LCD and stopping display data output by the LCD control circuit to be supplied to the LCD, when a vertical synchronous signal output by the LCD control circuit is suspended for a first fixed time; and   a power controller for stopping a power supply of the LCD, when a horizontal synchronous signal output by the LCD control circuit is suspended for a second fixed time;   wherein said screen controller comprises: a first counter for counting a number of pulses of said horizontal synchronous signal generated by the LCD control circuit, said first counter being reset with each pulse of said vertical synchronous signal; and   a first comparator for detecting passage of said first fixed time when said number of pulses of said horizontal synchronous signal becomes more than a first predetermined number;     wherein said power controller comprises: a second counter for counting a number of pulses of a dot-clock signal generated by the LCD control circuit, said second counter being reset with each pulse of said horizontal synchronous signal; and   a second comparator for detecting passage of said second fixed time when said number of pulses of said dot-clock signal becomes more than a second predetermined number.     
     
     
       2. A power saving circuit of an LCD (Liquid Crystal Display) unit having an LCD, said power saving circuit comprising: an LCD control circuit according to a VESA (Video Electronics Standards Association) standard, for controlling the LCD; and   a screen controller for turning off a back-light of the LCD and stopping display data output by the LCD control circuit to be supplied to the LCD, when a vertical synchronous signal output by the LCD control circuit is suspended for a fixed time, said screen controller comprising: a counter for counting a number of pulses of a horizontal synchronous signal generated by the LCD control circuit, said counter being reset with each pulse of said vertical synchronous signal; and   a comparator for detecting passage of said fixed time when said number of pulses becomes more than a predetermined number.     
     
     
       3. A power saving circuit of an LCD unit having an LCD, said power saving circuit comprising: an LCD control circuit according to a VESA (Video Electronics Standards Association) standard, for controlling the LCD; and   a power controller for stopping a power supply of the LCD, when a horizontal synchronous signal output by the LCD control circuit is suspended for a fixed time, said power controller comprising: a counter for counting a number of pulses of a dot-clock signal generated by the LCD control circuit, said counter being reset with each pulse of said horizontal synchronous signal; and   a comparator for detecting passage of said fixed time when said number of pulses becomes more than a predetermined number.